This project is concerned with the factors associated with the use or non-use of contraception among sexually active adolescent females 15-19 years of age and males 17 to 21 years of age. The major objectives are: 1) to identify factors associated with use and non-use of contraception; 2) to identify predisposing factors that lead to "always use" or "never use" of contraception; 3) to achieve greater precision in the measurement of contraceptive use in relation to situation factors and methods used; and 4) to analyze changes in sexual activity and contraceptive use among young females since a previous survey in 1976. The study involves personal interviews with a national probability sample of eligibles living in households in metropolitan areas (SMSAs) in counterminous United States; interviews will be conducted with 1,500 females and 1,000 males.